1. Field of the Invention
This invention relates to a rotation shaft seal.
2. Description of the Related Art
Conventionally, for sealing between a rotation shaft and a casing, rotation shaft seals such as an oil seal have been used. Each of these seals has a rubber lip portion sliding on a peripheral face of the rotation shaft with line contact.
In the conventional oil seal above, abrasion problems are not generated on the rubber lip as long as the rubber lip portion is dipped in oil (lubricant oil). However, depending on used state or condition, liquid of which component is mostly gaseous has to be sealed. In this state which is poor of lubricant oil, outer leakage is generated because the rubber lip is rapidly abraded, or rubber material is heat-degenerated (hardened) for the heat of rotational sliding and cracks are generated.
It is therefore an object of the present invention to provide a rotation shaft seal having long life in which early abrasion and crack are not generated even in the state poor of lubricant.